For safety reasons, it is desirable to provide dynamic braking for electrically driven wheelchairs in addition to a conventional mechanical brake. Basically dynamic braking involves connecting a resistance across the motor leads so as to be in series with the motor. The back electro-motive force (emf) of the motor is now shorted through this resistance and gently slows the motor to some predetermined rpm which is governed by the value of the resistances and the amount of inertia of the motor load.
The provision of dynamic braking resistances across the motor leads provides further advantages in the absorption of back voltage spikes. U.S. Pat. No. 4,157,123 issued to Everest & Jennings, Inc., the same assignee as the instant invention, is an example of such a dynamic braking system for wheelchairs.
Further safety and advantages could be realized if a system were provided enabling the slowing of the wheelchair to substantially zero rpm following the action of the conventional dynamic braking utilizing a resistance. Any such secondary braking action should "blend in" with the primary action to avoid any jerking. In other words, a smooth deceleration is most desirable.